Here are some of the behaviors I've noticed. This post isn't too helpful since I don't have a good way to reproduce any of this and I don't have much diagnostic information:

With 512 and 514 I was seeing

1) I see batteries stop charging and the csv shows an overtemp error. The batteries are cool (love it!). It seems to happen when I swap from a just charge battery to a new battery.

2) Batteries not recognized when I put them in the connector. The led lights white but nothing happens. If I pull the battery, wait a sec, and put it back in it starts.

3) I seem to have batteries "squirt" out of my fingers and fall to the floor way too much as I pull them out. The clips have a very aggressive spring force and I have to pull hard to get the batteries out.

If you can email me or post the CSV file from the SD card, that would be useful.

Some notes/questions:

What's your ambient temperature? I've recently had a couple of cells stop charging due to being over temperature, so I'm thinking about raising the maximum temperature limit.

There is a 10 second pause while the charger waits for you to push the button to indicate which sub mode you're wanting. If you don't push the button within 10 seconds, it will just start the standard mode automatically.

Yeah, I get that too. If I'm careful, it's not too much of a problem, but it would be nice if they weren't quite so strong, I agree!

I am ordering weaker spring clips right now. I used them in the past and struggled with which one to go forward with for this project. The only catch with the weaker clips, is that you may sometimes get bad contact and need to squeeze/readjust them with use.

You are right and so for those without cases I will probably still keep them the same. However when the case is on it is even harder to get them out of the death grip those clips have on your batteries.

Okay, I grabbed a charger with a case and one without. Did a test on both and there are flying cells either way. However you are right, you can somewhat leverage the battery out on the charger with a case especially on the SD card side. I wish they would loosen up with use, but not really. I did bend some out in the past and that helped a little.

I'm not too keen on the idea of the weaker clips needing to be squeezed/readjusted after they've seen a fair bit of use.

I think it would be better to try to adjust the current clips so that they're not hanging on so tight.

I wonder if it would be possible to find something that is just the right size to insert into each clip to stretch them enough but not too much? It's a bit hard to describe what I'm thinking of so maybe I should do a sketch, but I'm thinking of something like some mild steel that is rounded at the bottom, but then goes to straight vertical edges - so that it's relatively easy to insert but so that the clips don't close around it and make it hard to remove. A hole could be drilled and tapped so that a rod could be screwed in with a handle on the end. It would be a bit of a pain to make something like this, but it'd be easier than trying to manually stretch each clip just the right amount. Probably the hardest bit would be working out the right size to do the job.